Extron Electronics ES3610_11 User Guide - Manual (Page 56)

ES3610/11 User Guide Appendix B: Understanding VN-GLIMPSE Performance
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What can affect these criteria?
Data Stream ‘Bottlenecks’
The VN-GLIMPSE RGB ADAPTER only streams data relating to ‘changes’ in the source display.
Therefore, a source containing a lot of movement (e.g. an MPEG movie) will create more data than a
source with little or no movement (e.g. a spreadsheet file). Changes in latency or refresh rate can
arise when a ‘bottleneck’ occurs at some point in the data path which restricts the flow of data. The
potential bottlenecks are:
Data Encoding – Data from the source capture process is encoded into a VN-GLIMPSE data stream
and sent to the network. Under normal circumstances, the RGB ADAPTER is capable of encoding
most sources without any difficulty. However, if you are using a high resolution source containing a lot
of movement, the encoder may generate more data than can be transmitted between frame captures.
In this situation the encoder can temporarily reduce the refresh rate allowing more time for the data to
be sent. See ‘Adjusting the Encoder Parameters’ (page 58).
Network Bandwidth – This is the total volume of data that can be handled by the network at any
given time. If you have a high bandwidth network and only one RGB ADAPTER it is unlikely that you
will ever experience any problems. However, in extreme circumstances if you have a low bandwidth
network, a network with heavy traffic, or you are using several RGB ADAPTERs, you may find that the
available bandwidth is insufficient to cope during peak demand. It is important to note that the network
will only be as good as its weakest link. For example, if you have a 100BASE-T network with a
10BASE-T router, the effective bandwidth could be much less than expected.
Data Decoding – Whatever viewing platform you are using (i.e. the VN-GLIMPSE VIEWER running
on a computer or a VN-2400 Processor) the efficiency with which the data stream is decoded will
largely depend on the capacity of CPU (central processing unit). As with the encoding process, the
decoder can choose to reduce the refresh rate.
The most likely cause of a bottleneck here is by placing too much demand on the CPU, such that it
cannot decode the VN-GLIMPSE data stream quickly enough:
• If you are using the VN-GLIMPSE VIEWER, the CPU of the computer should be as fast as
possible. Also, remember that running other applications at the same time as the VIEWER will
create extra demand for the CPU.
•
If you are using a VN-2400 Processor, remember that the number of sources it is displaying
together with the content of those sources will impact on how much work the CPU has to do.
• Sources that are scaled up or down (rather than being viewed at their native resolution) will
require more CPU time. See ‘Source Scaling’ below.
Source Scaling
For optimum viewing, it is preferable to display a source at its native resolution (i.e. unity, not scaled).
This results in the viewed source being simply a pixel-for-pixel copy of the original. This keeps
processing to a minimum and ensures the best possible image quality.
Scaling a source requires each pixel value to be recalculated and, consequently, will place a high
demand on the CPU. This can lead to increased latency and reduced refresh rates as described
above. In addition, since each pixel is recalculated, the image may not appear as sharp as the
original. This will become more noticeable as the image gets smaller, especially if the image contains
fine detail.
HINT: Apart from the improved image quality provided by digital sources, they are also more
efficient on encoding. This is because analog sources invariably contain a certain amount of noise
and this can add to the overall content of the data stream. In addition, analog sources may produce
‘contouring’ effects during motion.